The overall objective of the proposed studies is to develop and characterize novel nucleoside-based inhibitors of glycosylation. Unlike classical glycosylation inhibitors that can be expected to affect all cells and have significant side effects due to this lack of specificity, nucleoside-based glycosylation inhibitors can be directed toward specific classes of cells and, therefore, provide an important new class of inhibitors. This goal is based on the fact that 3'-azidothymidine (AZT) potently inhibits lipid and protein glycosylation. The specific aims of the project are to: (1) Develop quantitative structure-activity relationships that describe binding of NMPs to nucleotide-sugar translocators. This information will then be used for the design and synthesis of nucleoside analogs that will potently inhibit glycosylation reactions when converted to the monophosphate, but will not inhibit DNA replication or repair if converted to the triphosphate; (2) Obtain a detailed description of the effects of AZT on lipid, N-linked, and O-linked protein glycosylation in whole cells to identify the process(es) most sensitive to AZT. Novel glycosylation inhibitors are highly relevant to a number of disease states. (i) Large changes in lipid and protein glycosylation are frequently associated with oncogenesis. Glycosylation inhibitors that specifically targeted cancer cells could be uniquely effective at controlling the growth of tumors. (ii) It may be possible to take advantage of the unique specificity of Herpes thymidine kinase to develop inhibitors that only accumulate in virus infected cells, block proper modification of viral proteins, and interfere with virus spread. (iii) Since effects on glycosylation are likely responsible for some of the toxicity of AZT when used to treat HIV, these studies may lead to strategies to control toxicity. (iv) It might also be possible to develop nucleoside-based glycosylation inhibitors that will affect both quiescent and growing cells. Such inhibitors could prove useful for treatment of a wide variety of conditions such as ganglioside storage diseases and inflammation.